The invention relates to an analog-to-digital converter, and more particularly, to an analog-to-digital converter used in a data readout system.
In modern circuit design, high speed analog-to-digital converter is important because of the need for transferring massive information from analog signals into digital signals. A Flash ADC is commonly used for converting analog signals into digital signals at a high speed. The high speed of a Flash ADC is achieved by parallel operation. Traditionally, 2n−1 comparators are used in an n-bit Flash AD converter. The 2n−1 comparators operate simultaneously and then the comparison results are encoded into an n-bit digital output. However, comparators occupy a large area in a Flash AD converter. The higher the resolution requirement is, the larger the area would be. For a data readout system, such as an optical drive, a great amount of data needs to be read from an optical disc and transferred into digital formats very fast and reliable. More comparators could increase resolution and accuracy, but suffer from large chip area and high cost. Thus, there is a need for a new analog-to-digital circuit with high accuracy, high speed, but with smaller area and lower cost.